Pokeweld gun



D. H. ESTES POKEWELD GUN June 18, 1946.

Filed Jun'e 10, 1944 S .n m m wwwggmy w m QN m5 i ATTORNEY.

Patented June 18, 1946 PATENT OFFICE POKEWELD GUN Donald H. Estes, Lincoln Acres, Calif.y assignor to Rohr Aircraft Corporation, Chula Vista, Calif., a corporation of California Application J1me l0, 1944, Serial No. 539,638

1 Claim.

My invention relates to pokeweld guns, and its objects are to provide a means within the gun itself for effecting impact of the welding tip both before and after the same is serving as an electrode of the welding circuit; to produce a better and more efficient weld than has heretofore been accomplished, particularly for the fastening together of sheet metal parts while the same are held in proper relationship upon a jig; to construct a pokeweld gun which is simple in construction, flexible as to movement and welding position, and'capable of being handled by an operator with a minimum of instructions, and in general to simplify and render more effective the construction of the several parts. Other objects will appear from the drawing and as hereinafter set forth and described.

To spotweld two pieces of metal together, there are two main requirements; first, such pieces must be held together with sufficient pressure in the welding area at the exact instant that the welding is accomplished, and second, an electric current must be available in suiiicient amount to heat said pieces to their melting temperatures in such welding area. To accomplish the necessary pressure, at the exact instant required, is an act'difflcult to bring about through the use of the usual handweld gun in the hands of an ordinary workman who, in attempting to apply such pressure manually through application of the welding tip to the work is, as a practical matter, unable to secure uniformity of result, and is almost certain to obtain a number of weak or imperfect welds. Furthermore, in the case of welding sheets of aluminum and its alloys, where relatively high pressures and temperatures are necessary for a proper and successful weld, it has been found impossible to secure any form of weld with prior handweld guns for a, proper and successful weld.

The production of sheet metal parts of aluminum alloys for airplanes, and other structures incorporating such parts, often requires that the parts be fastened together upon a jig. so that they will hold the proper relationship to each other while being welded. This fastening usually takes the form of drilling holes through the parts, filling these holes with bolts or rivets. and then removing the parts from the jig and spotwelding between the fasteners. However, with my invention I propose to fasten these parts together by tackwelding on the jig, the jig forming one electrode of the welding circuit and the other electrode being the welding tip of the pokeweld gun. In addition to supplying the other electrode, this gun also through an air actuated piston within the barrel of said gun furnishes the welding pressure or impact needed to weld aluminum or its alloys. 5 ily to position and can be handled by the ordinary workman with simple instructions. In addition to the gun, a timing device, a source of air under pressure and a source of electrical current are required to make the spotweld. Attention is hereby directed to the drawing, illustrating a preferred form of my invention, in which similar numerals of designation refer to similar parts throughout the several views, and

in which Figure 1 is a longitudinal section of my improved pokeweld gun, showing the hammer piston and barrel acting as piston cylinder therefor, air valve and connections for impelling said piston, solenoid, electric connections, and. mech- 10 anism for operating said valve, and welding tip serving as electric electrode and connecting parts; and

Fig. 2 is a section on line 2-2 of Fig. 1 looking in the direction of the arrows, and showing 85 the attachment of the cable for supplying electric current to the welding tip, and the air hose for supplying air under pressure to the piston cylinder.

Referring to the drawing, the barrel 3, which is the basic structure of my improved pokeweld gun, is made of copper, copper alloy or some other suitable electric conducting material. Closely fitting the bore of said barrel is the sleeve or lining 4, preferably circular in cross section, and serving throughout its length as a piston cylinder for the freely moving piston l8 therein. This piston IB is also made preferably circular in cross section so as to fit and to conform to the passageway of said cylinder, and is preferably made with a large central body portion, having at the front and back thereof and integral therewith the tongues or shanks l9 and 20, respectively, for the purpose hereinafter described. Opening outwardly from said passageway near the ends thereof are the ports 24 and 25, which are situated to make registration with ports 22 and 23, respectively, located near the ends of the hollow valve rod 2| sliding within the passageway 2m, which is formed within the wall of the basic structure of the barrel 3.

At the central portion of the passageway 2la and opening inwardly into the same is the air inlet port 26, connected by the fitting 38 to the air hose 3'', and registering with the slot 26a 55 extending through the wall of the rod 2|. Con-- The gun can be moved readwith outer end of the lever 28 and extending.-

through the opening 40, formed in the wall of the handle 6, is the armature 3| of the solenoid 39, the casing 32 of which is mounted-upon the outer side of the handle 6, and whichis provided I with the usual field coils 33; a compression spring 36 Within the hollow of said coils serving normally I to keep said armature in extended position.

At the outer end of the barrel 3 is formed the hollow nose 9, the bore of which is preferably provided Withthe lining or sleeve l0, and Which-is shaped to ,form a socket 13 for the shank l2 of the vtip holder H; the head of this tip holder having an opening forthe reception of the shank {15 of the welding tip l and being provided with a set screw I 6 extending through its wall and engaging with said shank to retain the same in operative position. As Wijll'bfl observed the inner end of thes-hank I2 extend inwardly o as nearly to fill the socket l3, which isshaped-to :per-

mit barelythe-entry of the front tongue or shank [9 of the piston 18 within the-said socket, as shown in dotted lines in Fig. 1; thereby permitting the said piston to strike a sharp blow upon the shank 12 when impelled against the-same in the-manner hereinafter set l forth. Both thesaid nose 9 and-the tip Mare of copper orother .electric conducting material and are preferably connected by a bonding cable 11. In the inner end of the gun, between the handles thereof, and I registering with the bore of the barrel 3, is the threaded opening 4|, within which is received the threadedshank of the plug 1, provided with the socket or cushion 8, shaped to engage with the tongue orrshank 213 of the piston 4 B.

apiece convenient to the'hand of the Opa ator, I preferably install-and secure to on of the handles 5 of my improved gun, the button switch which is operatively connected with con" vsei pna el ct ica timing devic m v e t h oug h suitable connections to control in any er well understood in the art the solenoid 39 and to control the current supplied through the cable 35. This timing device for firing the gun can be electronic or electrmmechanic'al in its design. Its functions, however,- remain the same regardless ofhow they are accomplished. When the operator has positioned the gun against the metal sheets upon the jig serving as a negative electrode, preparatory to welding, he pushes the button switch 35 on the handle '5. Thi switch sets the timing device into action. Up until the time the button is pushed, compres sion spring3 ha held the solenoid armature! in the positionshow-n in Fig. 1'. This armature has in turn held hollow valve 2,] in the position shown in Fig. 1 by means of eval-ve connecting rod 2] and lever .28. With the valve in this position, compressed air enters hollow valve rod 2! through air hose 3'! and air inlet port 25 and air occupying the space behind the piston is exhausted through rear port 25 into passageway Zia, past valve connecting rod 21, and escapes to the atmosphere. Upon reaching the rear of barrel liner 4, rear shank 20 of piston l8 enters the hollow of socket 8 upon the evacuation of said air, the general eiiect being to create an air cushion to prevent the impact of piston I8 from damaging barrel liner 4 or plu 1. Until the valve is again moved, the compressed air will now hold said piston in the rear of barrel liner 4.

When button switch 35 is pushed by the operator and held closed to set the timing device into operation, the first action of the timer will be to close the circuit of solenoid 38 to its current supply. This energizes the field coil 33 and magnetically attract-s armature 3| which moves hollow valve rod H to a position such that the front port 24 in barrel liner 4 is opened into passageway 21a, and thence to the atmosphere. .Atthis juncture, front port 22 in hollow valve rod 2] i closed andrear port 23 of said rod ,2! is aligned directly with rear port 25 of barrel liner .4, thus allowing compressed air topass through port- 23 and.25 to rear of piston l8. As theresult, the action .of the air will be to sendthe piston down the passageway of barrel liner 4.,at a high rate of speed until it strike the .faceof .the shank l2.of tip holder H. [This impactcoldtorrns or cups the sheets of metal tobe welded, thusxelosing their surface-resistance to a point-where it is practicable to weld. Shortly after thesaid impact, the timing device closes the circuit of the welding current allowing this current to fiow through welding current cable 36, throughcopper barrel 3, bonding cable 11,:Mbelding tip M, material to be welded andthe Jig r negative electrode, and back to the current source. welding .current is of sufiicient quantity to heat the sheets-of metal to the ,point effusion in the spotweld area The weldingcurren-t circuitremaining ,closedfpr a small traction .of -a second, it is then opened by the timing device-sim lta-v neously with opening of e the -.solenoi d circuit, ,allowing spring 343 to return the hollow valve .24 --to its-original position and .theipiston L8 again ,to be returned to .the rear of barrel liner 41in the m nn r. r sl cpb dmm. a e-1 u on the piston ,LB reaching the rear of barrel liner the timing device again closes the solenoid pircuit, sending piston 3 down barrel liner 4 until impact with -tip holder shank I2 is attained After thi impact, the solenoid circuit is aga n opened, allow l the piston to returnto rear of barrel liner A as -.Previons1y described. Thepurpose .of this second impact isto forge the weld,

thus refining the crystalline .grainstructure and that all that is required to weld again i thatope-rator again hold button switch 3 5-elesed; During the entire operation, only sufiicien-tcbpdy pressure to hold the gun 'in position is .requiredof he-op ra or- The sequences following th pressure of the No further welding or timer action button 35 are mechanically or electrically operated without control by the operator, except that he is allowed to place the gun in welding position to effect the desired weld. Generally speaking, the first impact of the gun produces a slight cup or dimple and accomplishes approximately a one hundred per cent close touch of the two sheet metal parts over the contact area. This result makes it unnecessary for the operator to exert the pressure required in the operation of the prior handweld gun as employed by the ordinary workman. With my improved gun, such contact is brought about mechanically or electrically as aforesaid without said required exertion, and shortly after said contact or a small fraction of a second thereafter, the welding current is turned on momentarily to weld together automatically the two touching surfaces by reason of the aforesaid action of th timing unit. Th last step of the sequence is again to produce automatically an additional impact upon the weld while it is still up to forging temperature; resulting in a final weld of better grain structure than has been obtained heretofore and resulting consequently in higher fatigue and tensile strength.

By the words pokeweld gun as used in this specification and claims, I desire to be understood as meaning a portable welding gun capable of being readily carried and held in the hands of the usual operator, and containing an electrode in the form of a welding tip and being provided with piston means capable of exerting impact pressure upon said tip.

My invention may be embodied in other speciflc forms without departing from the spirit or essential characteristics thereof. The present embodiment, as above set forth, is therefore to be considered in all respects as illustrative and not restrictive, the scope of my invention being indicated by the appended claims rather than by the foregoing description, and all changes which may come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

What I claim and desire to secure by Letters Patent is:

In a pokeweld gun, the combination of an electrode in the form of a barrel having an elongated enclosed passageway therein with inlet and outlet ports communicating with said passageway, a Welding tip secured to one end of said electrode and forming part thereof, means for controlling and for temporarily energizing said electrode to effect a weld through said welding tip, a piston disposed within and shaped to make close sliding contact with said passageway, a sliding valve secured to said barrel for opening and closing said ports, a solenoid connected with said barrel for controlling said valve and for admitting and expelling air into and out of said passageway through said ports and causing said pis-= ton to be driven along said passageway and to efiect striking impact upon said tip and thereafter to move away from the same, and means for controlling and temporarily energizing said solenoid.

DONALD H. ESTES. 

